3 Cylinder 70's 80's 60hp-70hp interchange questions 49.8cu.i.

[mixerjv]

I have obtained a Mercury 1987 60hp 3cylinder that had been submerged and the block is shot.

I also have a late 70's 3 cylinder 70hp block, which I would like to use as a replacement. (for those who don't know: Mercury went from crankshaft HP to propshaft HP in the mid eighties and the 70hp became the 60hp)

I can't find the serial number on the older block, anyone know if/where they stamped the numbers?

I'm trying to ascertain the differences. I was surprised to learn that they installed thermostats in the older 3 cylinders, but omitted them after around 1980.

They also changed the firing order from 123 to 132. I will have to be careful wiring the switchbox.

Anyone have any insight on other issues? Can I omit the thermostat?

 

[achris]

Re: 3 Cylinder 70's 80's 60hp-70hp interchange questions 49.8cu.i.

If it's not on a aluminium plug on the block, it might be stamped into the top of the block.

Chris........

 

[Faztbullet]

Re: 3 Cylinder 70's 80's 60hp-70hp interchange questions 49.8cu.i.

The block dont care about firing order..it the crank that cares. As long as the late 70's block had ADI ignition it will work, if it had the distributer will not work.

 

[mixerjv]

Re: 3 Cylinder 70's 80's 60hp-70hp interchange questions 49.8cu.i.

Thanks for the replies. No welch plug like the '87. No serial number on top. Definitely ADI. Cone shaped fuel filter, which places it between '76 and '79. Looking at the parts lists my only worry was the '76 (65hp) is a unique animal, and is also different between the long shaft and short (no idea why), and half of '77 is unique, with the second have common upwards.

 

[mixerjv]

Re: 3 Cylinder 70's 80's 60hp-70hp interchange questions 49.8cu.i.

AND THE MYSTERY block deepens, it appears my late70's block has a physical firing order of 1-3-2, not 1-2-3 as labeled on the head cover, and assumed by model year clues.

It must have been rebuilt as some point and a later model crank installed.